Photographic fixative composition containing boric acid esters of polyhydric alcohols of at least six carbon atoms



Patented Sept. 15, 1942 UNlTED STATES PATENT OFFICE PHOTOGRAPHIC FIXATIVE COMPOSITION CONTAINING BORIC ACID ESTERS OF POLYHYDRIC ALCOHOLS F AT LEAST SIX CARBON ATOMS Charles Holzwarth, ParlinQN. J., assignor, by

mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application April 10, 1941, Serial No. 387,976

16 Claims. (Cl. 95-88) Anobject of this invention is provide a practical photographic fixing solution in concentrated form. Another object is to provide a concentrated photographic fixing solution, the ingredients of which remain in solution over a wide range of temperature conditions. object is to provide stabilizing agents which will inhibit crystallization and/or precipitation in highly concentrated photographic fixing solutions. A further object is to provide agents which have a stabilizing effect on concentrated photographic solutions, but do not have an adverse effect on the photographic functions of such solutions. A.

still further object is to provide new processes of stabilizing concentrated photographic soluents. uses for soluble borates of polyhydric alcohols containing at least 6 carbon atoms in the'or-- ganic radical or radicals attached to the borate radical and the water-soluble salts thereof.

The above-mentioned disadvantagesv can be overcome and the above objects attained by the use of boric acid esters of polyhydri-c alcohols containing at least 6 carbon atoms in photographic fixing compositions. To be more specific, it has been found that photographic fixing compositions containing water-soluble salts of thiosulfuric acid as the fixing agents can be improved by the addition of a boric acid ester of a polyhydric alcohol containing at least 6 carbon atoms including the neutral esters,- acid esters and water-soluble salts of acid esters.

In amore limited sense, the invention involves the preparation and use of photographic fixing compositions comprising a saturated or supersaturated solution of a soluble salt of thiosulfuric acid and an amount of a boric acid ester of an aliphatic polyhydric alcohol containing at least 6 carbon atoms in a straight chain and at least 6 hydroxyl groups including the neutral esters, acid esters and the alkali metal and ammonium salts of acid esters.

The concentrated photographic fixing baths hereof can be prepared by admixing the thiosulfate in an amount suflicient to form a concentrated solution and stabilizing amounts of the Yet another aforedescribed boric acid ester compounds. In a preferred procedural aspect, a concentrated photographic fixing bath is prepared by dissolving a quantity of a boric acid ester of a polyhydric aliphatic alcohol of at least 6 carbon atoms, in a saturated or supersaturated solution of a soluble thiosulfate fixing agent. 'The solution may be made facile by the aid of a moderate amount of ,heat, e. g. temperatures of 50 to 'C., and agitation.

Another practical 'Way of making the concentrated photographic fixing baths comprises warming a concentrated aqueous solution of the dried thiosulfate or mixture of thiosulfates and adding it to a vessel containing the predetermined quantity of the :boric acid ester compound derived from a polyhydric alcohol containing at least 6 carbon atoms.

The solution may then be augmented by the addition of other common ingredients of fixing compositions; e. g. anti-staining, hardening and/or preserving agents, acids, etc. Among the latter agents mention might be madeof soluble sulfites, e. g. alkali metal, ammonium, substituted ammonium, and amine sulfites, alums, organic acids and easily hydrolyzable salts, sulfami-c acids and other materials which have been added to increase the life, penetration and usefulness of photographic fixing solutions.

It has been found that solutions prepared as described above are remarkably stable and are not subject to the expected crystallization or precipitation of dissolved solids which usually occurs when such solutions are cooled. This stability is not impaired by storage or agitation, even at reduced temperatures over a considerable period of time; and such solutions were found to fill all the requirements of a concentrated liquid fixer. As crystallization and precipitation follows rapidly in superstaturated solutions such as have been described free from the novel boron compounds hereof, it may be supposed that such compounds of polyhydric alcohols act as crystallization inhibitors.

The invention may be used with any salt of thio-sulfuric acid which has photographicfixing properties and indeed in any type of fixing solution, wherein a thiosulfate is an essential fixing agent. 'I'hiosulfates which may be conveniently used with the novel stabilizing boron compounds hereof include 1) alkali metal thiosulfates, e. g. lithium, sodium and potassium thiosulfates, (2) ammonium and substituted ammonium thiosulfates and (3) organic amine salts of thiosulfuric acids, including those of primary, secondary, tertiary and cyclic amines, and (4) amidine thiosulfates, etc.

The .boric acid esters and alkali metal and ammonium salts used in accordance with the teachings of this invention may be prepared by reacting at least about one mol of a polyhydric aliphatic alcohol containing at least 6 carbon atoms with 1 mol of a boric acid in an aqueous medium and heating the mixture until two mols of water are lost. The alkali metal and ammonium salts can be made. by the addition thereto of alkalies such as ammonia, ammonium hydroxide, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.; or the required amount of an alkali metal borate can be substituted for the boric acid in the reaction mixture.

While satisfactory results are obtained with the boric acid ester free from salt groups, ithas been found that improved results can be obtained with the alkali metal and ammonium salts of such borates and still further improved results obtained from the alkali metal and ammonium salts of boric acid esters of hexahydric alcohols or hexitols.

When referring to salts of polyhydric esters such as sodium mannitol monoborate, sodium sorbitol monoborate, etc., it is understood that such terminology is used to describe any polyhydric ester that has been partially or entirely reacted with an alkali metal hydroxide or ammonia. In such cases the substance is frequently a mixture of the original boric acid ester of the polyhydric alcohol and the sodium salt of such in ester. This is usually the case because the practice is to add just enough of the alkaline material to give a solution with a pH of 7. At this pH reading, only part of the original ester is converted to the salt. The preparation of suitable boric acid esters, including the salts is more fully described in U. S. Patents 2223349,

2,223,948, 2,223,949 and 2,224,011 and British Patent 511,641.

The proportions of ingredients can, of course.

that concentrated fixing solutions which contain not less than 60% by weight of active fixing bath ingredientscan be efiectively-stabilized against precipitation or recrystallization of dissolved ingredients by incorporating therein not less than 8% of a boric acid ester of a polyhydric alcohol "of at least 6 carbon atoms including the alkali 'metal and ammonium salts of such esters.

The invention will be further illustrated, but is not intended to be limited by the following examples. In each example the thiosulfate salt is first dissolved in about half its own weight of water at a temperature somewhat above C. and then the organic borate is dissolved in the resulting solution. After thorough incorporation of the borate, the remaining ingredients are each added in the order in which they appear in the formulae and dissolved with vigorous stirring. If difliculty is experienced in dissolving these latter constituents they may be dissolved in a minimum of warm water before adding to the solution. The final volume of the concentrated fixer is brought in each case to a volume be varied over a wide range. It has been found 5 pending on the type of adjustment the formula requires.

The above bath when diluted with 3 liters of water can be successfully used in conjunction with a 3% chrome alum stop bath.

Example III Ammonium thiosulfate (anhydrous) grams 600 Ammonium mannitol diborate (pH 7) do Potassium sulfite (anhydrous) do 65 Propionic acid do 60 Potassium alum; do 60 Sodium metabisulfite do 5 Water to make milliliters 1000 Example IV Triethanolamine thiosulfate grams 550 Sodium sorbitol monoborate (pH 7) do Ammonium sulfite do 40 Sodium metabisulfite do 8 Citric acid do 10 Potassium alum do 55 Water to make milliliters 1000 Example V Ammonium thiosulfate (anhydrous) grams 560 Ammonium dulcitol monoborate (pH 7) I do Sodium sulfite (desiccated) do 40 Potassium bisulfate do 20 Citric acid do 10 Formaldehyde do 40 Water to make "milliliters" 1000 Example VI Ammonium thiosulfate (anhydrous) grams 580 Sodium mannitol monoborate pH '7) do- 100 Sodium sulfite (desiccated) do 55 Sodium metabisulfite do 10 Lactic acid do 75 Water to make milliliters 1000 of 1000 ml. by concentration or dilution, de- 75 This concentrated fixer may be diluted for use by adding to it 3000 milliliters of water to which have been added 65 grams of A1Cl3.6H20.

I 2,295,734 Example VII accordance with the teachings hereof. In general, Guamdme tmosulfate "grams" 565 t least y wei ht of the compounds is neces- Ammomum sorbitol monobomte (pH 7) sary in concentrated fixmg compositions contam- 105 ins not less than 60% by weight of active fixin Sodium sumte (desiccated) 40 bath ingredients for satisfactory results. Amounts Acetic acid (glacial) 35 from 8 to 50% constitute a practical range. Potassium alum 60 The boric acid esters described herein can be Water to make "milliliters" 1000 used in dry fixative compositions which can be diluted to form concentrated fixing solutions or x p VIII 10 fixing baths. Ammonium thio ulfate (anhydrous) Similarly, in place of the specific thiosulfates 1 grams 57 mentioned in the above examples, may be sub- Mannitol monobollate (acid) 200 stituted one 01 more other water-soluble thiO- Sodium Sumte (desiccated); 55 sulfates including alkali metal, ammonium and Pmpmmc acid 60 substituted ammonium thiosulfates. The sulfites Potassium alum 65 of the examples can be interchanged in any de- Sodium metabisulfite do 5 Wed mannerv Water to make "milliliters" 1000 A large number of suitable substituted ammonium thiosulfates and their preparation is 'de- Ewample IX scribed in a copending application of Martin Sodium thiosul'fate (crystalline) g'rams s50 Mara-s00. entitled Preparation of Ammonium Sodium sorbitol bomte (pH 7 o 125 Thiosulfates and Uses Therefore", Serial No. Ammonium sulfite 40 390,980 filed upon an even date herewith. These potassium metabismfite 10 substituted ammonium thiosulfates have the can i 10 general form la: Water to make "milliliters" 1000 R1\I|t This concentrated fixer may be diluted for use N 3291 by adding to it 3000 m'lliliters of water to which, have been added 65 grams of AlCl3.6H2O.

Example wfhirtsin R, R1, Ratand cgnstitute guslmgers o e group consis mg 0 y rogen an y ro- 2 1353 1 u m t hi 0 S ul f a t 8 23235? 680 carbon raidtilcals, wheil'ein two t1? tzhree1 ofttthedRs may cons i u e a sing e monooriva en y rogggl fig ggfi g figg (pH 7) g;' carbon radical. To be more specific, R, R1, R2, Potassium metabisumte "1 10 and R3 may constitute a hydrogen atom or a Sodium acetate 40 hydrocarbon radical or two or more of the Rs Acetic acid (gla 40 together form a carbocychc hydrocarbon radical Water to make ::11 fifiiters 1000 This concentrated fixer may be diluted for use with a solution of dissolved in a sufilcient quantity of water to make 3000 milliliters.

Example XI Ammonium thiosulfate (anhydrous) grams 560 Sodium sorbitol monoborate (pH 7) do 80 Sodium sulfite (desiccated) do 30 Acetic acid (glacial) Q. do 15 Sodium metabisulfite do 5 Water to make mi1liiiters 1000 This :solution may be diluted for use by the additionof 3000 milliliters of water to which have been added grams of AlCl:.6H2O.

In place of the specific boric acid esters set forth in the above examples may be substituted a large number of equivalent boric acid esters having the characteristics above set forth. The boric acid esters of the respective examples can be interchanged in any desired manner. One or more of the esters mentioned above can be used in each example. In addition, one or more of each of the boric acid esters hereof can be substituted in each of the above examples.

Additional suitable boric acid esters include the neutral and basic alkali metal or ammonium salts of the condensation products of boric acid compounds with 1,2,3,4,5-pentahydroxy hexane; heptahydric alcohols, e. g. perseitol and volemitol; octahydric alcohols, e. g. octahydroxy-octanes; nonahydric alcohols, e. g. nonahydroxy nonane, etc. These compoundsand others which are described in the above-cited patents, are useful in grams of potassium alum other substituents dodecyl, n-tetradecyl,

or a heterocyclic hydrocarbon radical with the nitrogen atom. Thus, one or more of R, R1, R2 and R3 may be primary, secondary, tertiary, iso or branched chain alkyl radicals of l to 20 and more carbon .atoms; cycloalkyl of 3 to 6 and more carbon atoms, which may contain hydrocarbon and in the carbocyclic ring; aryl of 6 or more carbon atoms; aralkyl of '7 or more carbon atoms, and R and R1 may form a cycloalkyl radical or aryl radical or a part of a chain which with the nitrogen atom forms a heterocyclic radical.

Suitable alkyl radicals for the values of R, R1, R2, and R3 are methyl, ethyl, propyl, isopropyl, normal, primary, secondary and tertiary-butyl, -pentyl and -hexyl, Z-ethyl, hexyl, n-decyl, n-

n-octadecyl, etc. Suitable cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl, dodecylcyclohexyl, chlorocyclohexyl, etc. Suitable aryls include phenyl, chlorphenyl, tolyl, xylyl, nephthyl, chloronaphthyl, etc., and aralkyls include benzyl, chlorobenzyl, menaphthyl, etc. However, at least one hydrocarbon radical must be attached to the pentavalent nitrogen atom.

Such substituted ammonium thiosulfates and organic amine salts of thiosulfuric acid are advantageously prepared by the action of sulfurdioxide on a polysulfide of an ammonium or or ganic amine base in the presence of an excess of the free hydroxideof the particular ammonium or amine radical whose thiosulfate is desired. Sumcient sulfur dioxide is employed to consume entirely the sulfide ions in the original solution,

and the reacting mixture must be maintained in a slightly alkaline condition throughout the entire course of. the reaction.

Various other ingredients of photographic fixing compositions may be utilized in compositions similar to the above. citric acid, sodium citrate, sodium acetate, sodium amino acetate, etc., which yield borate, citrate, acetate, amino acetate, etc., ions, other sulfamates, e. g. N-alkyl acids, e. g. N- methylsulfamic, N-ethylsulfamic, N-propylsulfamic, N-diethylsulfamic, N-dimethylsulfamic, etc., acids.

The addition of small quantities of other acids, such a s tartaric, fumaric, malic, maleic, lactic,

The compositions of this invention are useful for fixing baths which are of general utility in the photographic arts. Thus, they may be utilized for processing ordinary camera, film,

preparation of concentrated fixing solutions containing more than 60% by weight of dissolved A further advantage is that stable solucrystallizing out of solution during storage or shipment. A still further advantage is that the invention permits the stabilization of highly concentrated solutions of ionized compounds against precipitation.

As many apparently defined by the appended claims.

I claim: 1. A fixative composition comprising an aqueous solution containing a soluble thiosulfate fixing salt and at least one ester of a boric acid with a polyhydric alcohol having at least 6 carbon atoms and 6 hydroxyl groups.

2. A fixative composition comprising a con- 6 carbon atoms.

5. A trated aqueous solution containing a soluble thicleast 6 carbon atoms, and at least 6 hydroxyl groups.

7. A concentrated aqueous bath containing more than photographic fixing 60% by weight of 8. A concentrated aqueous photographic fixing bath containing more than 60% .by weight of active acid with a hexitol.

14. A concentrated aqueous photographic fixins bath less than 8% by weight of at least one ester of a boric acid .with a hexitol.

'16. The process which comprises? fixing a in an amount suflicient to prevent the precipitation and crystallization of the ingredients, at 40 F.

-15. A concentrated aqueous photographic fixing bath containing more than 60% by weight of active ingredients comprising essentially an acid and a soluble thiosulfate fixing agent, not

I photographic element in a bath of the type de- 5 fined by claim 1,

CHARLES HOLZWARTH. 

